Process for extracting metals from ores



Patented June I, 1937 I UNITED STATES PB OCESS FOB nx'ris r r me METALSFROM Carl Goetz, Berlin, Germany No Drawing. Original application March21,

1933, Serial No. 868,100, Divided and this Illpfleation June 1'], 1935,Serial No, 27,124. In

Germany April 1, 1932 6 Claims. 15

This application is a division of application Ser. No. 663,100, flledMar. 27, 1933. Bald patent has since become Patent 2.045.226, grantedJune 23. 1936. v

This invention comprises a process which is a development of my processfor obtaining metals from bituminous ores by heat treatment in theabsence of air and of my process for obtaining metals from sulphidicores by heat treatment in the presence of solid, liquid or gaseoushydrocarbons in absence of air. By bituminous ores are meant ores which,apart from the ore content, can be spoken of as bituminous rock, moreparticularly as bituminous shale, e. g. Mansield copper, shale, whichcontains 17% of bitumen hydrocarbons. 1

In the course of work carried out to bring these processes to perfectionit has been found that with certain presuppositions the metalscan alsobe liberated from their compounds without the action of the gases whichare evolved from bitumen, or gases of other kinds, lithe ores aresubjected to a heat treatment in an inert gas. with exclusion of air.The metals can be. liberform of iron oxides or metallic iron. For this.

30 purpose the iron-containing ore in the form of small to fine granulesis subjected to several hours heat treatment with exclusion of air in aninert gas or inan inert gas mixed with a combustible gas such ashydrocarbons, carbon monoxide and the like; i

It has been found that besides streams of inert gas, alone or mixed withreducing gas. any other non-oxidizing gas can be used for carrying outthe process. using such gases also the presence of iron oxides, metalliciron,

droxide of iron which form oxide of iron when heated, acts pre-eminentlywith a desulphuriz- 1 34% CO2; 0.2%0z; 17-18% co; 4a-5o%'m:

16-18% cm a a 55 In the case of copper glance which has been orsubstances like carbonate of iron and hymixed with iron oxides the yieldof metallic copper in the case of these gases is, other conditions beingequal, the same as when using an inert gas stream or a stream of inertgas mixed with reducing gas. Reducing gases are !re- 5 quently easier toprocure and cheaper than inert gases or mixtures of these with reducinggases. It is true they also exert a desulphuriz ing eflect without anyiron being present, but then considerably larger quantities of gas and10 longer reaction times or substantially higher temperatures arenecessary. For example, from 5 grams of finely ground copper glancewhich has been exposed for two hours at 600 C. to a steam-illuminatinggas stream flowing at a rate 15 01' 12 litres of gas per hour and 125cc. of steam per hour, only 0.9% otimetalliecopper is obtained whilstwhen using double the quantities of gas: and steam only 3.7% of copperare obtained in the same timeand at the same temperature.

I! the same quantity of copper glance is mixed with iron oxides inthe'ratio of 1:1, then other conditions being the same, after 2 hourstreatment at 600 C. in a stream of illuminating gas andsteam of 12litres of gas per hour and 125 cc. of water per hour, 65.2% of metalliccopper are produced. Since the reducing gases are only very slightlyused in this process, they canbe employed repeatedly. if necessary beingeach time purified from thesulphur dioxide or sulphuretted hydrogenamounting to only aiew percent of the original sulphur content of theore. The-best results are obtained at tempera-'- tures lying round about600 C. and by a further treatment at temperatures rising to about 800C., but the reactions already commence at lower temperatures. Thetemperatures must not be carried as high as the melting points of theminerals cominginto question or of the eutectic 40 mixtures present.It'has been proposed to dissociate antimony sulphide in a closed retortat temperatures 011500 0,, sulphur vapours escaping' and the separatedantimony flowing back into the dissociation chamber. It is also known todecompose pyrites and other sulphidic ores in indiilerent gases intotheir components by heating to fusion temperatures of "1500 to 2000 C.Further, it. is known to fuse partially roasted'copper matte or copperore with silicic acid and to obtain an enriched copper regulus,ironexe'rting a desuiphurizing eflect on lead sulphide and-a doublesilicate of lead'and iron then I being formed. The present invention isa substantial improvement over these known processes since all thelatter operate with substantially higher temperatures and employ liquidfurnace charges.

The process is suitable for every kind of sulphide and arsenide ore,more particularly for sulphidic copper ores, which in addition alsocontain noble metals such as gold and silver. The goldiand silvercontent of those ores which are to be regarded as goldand silver-bearingcopper ores also acts particularly favourably. Among other ores, ores ofthe Boliden Mining Comany were treated with the greatest success. Theores consisted of goldand silver-containing iron pyrites and arsenicalpyrites the copper being present in the form of copper pyrites. Thecomposition of the ore was as follows: 41.3% S, 1.88% Cu, 4.13% As, 32g/t Ag and 4 g/t Au. This ore was subjected to a heat treatment in acurrent of nitrogen, first of all for 6 hours at 600 C. and then for 4hours at 800 C. Whereas no noble metals could be seen in the originalore under the microscope, coarse particles of free gold and free silvercould be detected in the heat-treated material after 10 hours treatment,and indeed already after 6 hours. By the treatment at 600 C. the coppercontent was for the greatest part likewise liberated in the form ofmetal, but a part remained combined in the form of copper pyrites atthis temperature. In the further treatment up to 800 0., this copperglance also was for the most part decomposed with liberation of metalliccopper, whilst the particles of noble metalare coarsened further.

The process can also be employed for sulphidic and arsenic ores of everykind. Iron must be added in the form of iron oxides or other substancesfor which sulphur at the temperatures coming into question has a greaterafilnity than for the metals being recovered, or even iron sulphide maybe added. The copper can be wholly, or for the most part, liberated inthe form of metal from copper glance, which undergoes no change whenheated with the exclusion of air, by adding iron oxide powder. Thesulphur liberated deposits in the form of elementary sulphur or combineswith the iron. Sulphur dioxide escapes as well. The process can also beemployed together with a process for obtaining metals from bituminousores by heating the same with exclusion of air. The gases forming fromthe bitumen, or other gases, need then be used to only a small extentfor the desulphuri-.

zation or dearsenification of the ores, whilst the greater part of themetal is already liberated without the influence of these gases. I

In the treatment of artificial and natural bomite in a stream ofnitrogen, as well as in a stream of illuminating gas and steam, it wasfound that this ore is no longer stable at temperatures above 600 C. butis decomposed into metallic copper and copper sulphide, (copper glance).From artificial bornite, containing 98% copper in theform of CllsFeSs,0.7% copper in the form of C1138, 0.3% metallic copper, and 1% copper ascopper pyrites and containing no other constituents, 26.9% of metalliccopper were liberated after one hours treatment of the finely granulatedore in a porcelain boat in a stream of nitrogen, 2.6% of copper werecombined in the form of bornite and 70.5% of copper inthe form of coppersulphide. The reaction is accelerated if finely divided metallic iron isadmixed with the bornite. Artificial bornite of the kind describedabovemixed with metallic iron the proportion of 1:1 already yielded 55%copper in the form of metal after 2 hours treatment in a porcelain boatin a current of nitrogen. (Copper glance alone, as stated in "Metall undErz", 1932, page 112, is not decomposed when heated in an inert gas upto 1310' C.)

Natural bornite consisting of 70% CuaFeSa, 7.0% CuzS, 13% FeSz and 10%FezOa after two hours treatment in a boat made of brass gauze in astream of illuminating gas and steam at 600 C. yielded 85.4% metalliccopper and 14.6% in the form of CuzS, no more CllaFES: being present.After two hours treatment of natural bornite at 600 C. in a porcelainboat in a stream of illuminating gas and steam only 74.4% of metalliccopper are formed. After two hours treatment at 800 C. in a porcelainboat in a stream of illuminating gas and steam 78.1% of metallic copper,no bornite, and 21.9% of copper results are obtained by the treatmenteven in an inert gas (nitrogen) at the same treatment temperatures andwith the same treatment times.

CllzS intimately mixed with artificial iron oxides in the proportion of1:1 and heated in a porcelain boat. for two hours at 600 C. in a streamof nitrogen already yielded 46.9% in the form of metal whilst 53.1%remained combined in the form of C1128. No copper pyrites or bornite wasformed.

Culs and finely divided metallic iron mixed in the proportion of 1:1heated in a porcelain boat fontwo hours in a stream of nitrogen at 600C. yielded 64.2% of metallic copper and 35.8% of copper in the form ofC1128. No sulphur was -liberated but was taken up by the iron with theformation of ferrous sulphide. After two hours treatment of the samemixture in a porcelain boat at 800" C. in a stream of nitrogen 72% ofmetal were formed. After two hours heat treatment of the CuiS-metalliciron mixture (ratio 1:1) in a boat of brass gauze in a stream ofnitrogen; 99.2% metal were formed thesame granule size in the ratio of1:1 and the mixture subjected to two hours treatment in the absence ofair at a temperature at 600 C. in an atmosphere of nitrogen, thenalready of metallic copper are formed, but, of course, in a very muchfiner state of subdivision than is produced by the treatment of coarsergranules in a stream of gas.

The present process is also of considerable importance for oresof gold,silver, and copper which contain arsenic. These ores can be very simplytreated since the arsenic is wholly or for the greater part combinedwith the iron or iron sulphide'whilst the useful metals, such as gold,silver, copper and so forth are liberated in a 7 the metallic form. Thisis of particular importance for ores of the Swedish Boliden ore type,the economical treatment of which has hitherto been beset withdifficulties since the large quantities of arsenic which arise cannot beworked. The combination of the arsenic is brought about by admixing ironin the form of finely ground iron oxides, or the like. Other substancesscan also be used in place of iron oxide. For example, calcium oxide is asuitable such substance. Treatment in a carbon monoxide stream or astream containing carbon monoxide and nitrogen is particularly suitablefor such ores.

A temperature of 600 C. has been found to be particularly favourable,but equally good results are obtained at higher and lower temperatures;

I it is advisable, however, to avoid temperatures at whichresulphurizing of themetals to be obtained takes place. This temperaturefor copper is about 900 C.

In the treatment of Boliden ores, which have been intimately. admixedwith finely ground! iron oxide in the proportion of 1:1 and comminutedto a granule size of 1 mm., no arsenic escaped at all in six hourstreatment at 600 C., only very small quantities in ten hours treatment,whilst copper, gold and silver were liberated in the form of coarsemetal granules.

The addition of iron oxide may also be effected by dead-roasting a partof the ore and adding it to that portion of the ore which has not beendead-roasted.

Further, the treatment time is of importance.

It has been found that if the treatment time is too long the equilibriumis shifted into the opposite direction and re-formation of coppersulphide takes place. The liberated elementary metals can be worked upwithout difiioulty either 4 by gravitational methods or by flotation, orby chemical methods such as lixiviation and so forth. More particularlythe particles of ore,

subdivided in a state of colloidal fineness, may be conglomerated tosuch coarse particles that 4 they offer no further diflculty to theworking up operations. It is particularly noteworthy that the granulesize can be regulated according to the time of treatment insuch a waythat coarser particles are formed with longer treatment times 50 orhigher temperatures. This fact is ot particoxide to the ore in order torectify the defl-' ciency of this metal in the ore, and in heating themixture in a non-oxidizing, gas stream at an elevated temperature whichis substantially 65 below the melting point of the ore, whereby thesulphur and arsenic combine with the iron which is present and thenon-ferrous metal is liberated in its elementary state and conglomeratedto coarse particles.

2. A process for obtaining non-ferrous metal from iron-containing oresthereof of sulphidic 5 or arsenical nature, consisting in adding ironoxide to the ore in order to rectify the deficiency of this metal in.the ore, and in heating the mixture in a stream of inert gas at anelevated temperature which is substantialLy below the 10 ture in astream of inert gas mixed with a reducing gas at an elevated temperaturewhich is substantially below the melting point of the ore, whereby thesulphur and arsenic combine with the iron which is present and thenon-fer- 25 rous metal is liberated in its elementary state andconglomerated to coarse particles. 4 I

4. A process for obtaining non-ferrous metal from iron-containing oresthereof of sulphidic or arsenical nature, consisting in adding iron 30oxide to the ore in order to rectify the deficiency of this metal in theore, and in heating the mixture in a stream of reducing gas atanelevated temperature which is substantially below the melting point ofthe metal contained 35' therein, whereby the sulphur and arsenic combinewith the iron which is present and the non-ferrous metal is liberated inits elementary state and conglomerated'to coarse particles.

5. A process for obtaininghnon-ierrous metal 40 from iron-containingores t ereof of. sulphidic or-arsenical nature, consisting in addingfinely ground iron oxide to the ore in a quantity such that the mixturecontains suflicient iron to combine with the greater part of the sulphurand of the arsenic, and in-heating the mixture in a non-oxidizing gasstream at an elevated temperature which is substantially below themelting point of the ore, whereby the sulphur and the arsenic combinewith the iron which is presentand the non-ferrous metal is liberated inits elementary state and conglomerated to coarse particles.

' 6. A process for obtaining non-ferrous metal from iron-containing oresthereof of sulphidic 55 or arsenical nature, consisting in dead-roastingsome,of the ore, mixing the dead-roasted produotwith ore which has notbeen so treated, and

in heating the mixture in a stream of inert gas at. an elevatedtemperature which is substantially below the melting point of the ore,whereby the sulphur and arsenic combine with the iron which is presentand the\non-terrous metal is liberated in its elementary state andconglomerated to coarse particles.

v CARL eorrrz.

